36 Functional Description TB7100 Service Manual
© Tait Electronics Limited October 2005
3.4.12 Receiver Inhibit
The receiver inhibit input on the SYSTEM connector is used to control the
receiver gate signal. This may be used in linking applications to prevent
unwanted receiver audio signals from appearing at the SI board output
connector.
3.5 Fan Operation
The cooling fans are mounted behind the front panel. Both fans in the
chassis must be of the same type.
Dissipation of Heat Heat needs to be dissipated from a number of components on the transmitter
and receiver boards, including the following:
■ 9V regulator
■ RF PA
■ driver for RF PA
■ audio PA.
The mechanisms by which the heat is conducted away in each case are
described below.
Dissipation of Heat
from Transmitter
The transmitter board is mounted directly onto a heatsink through which
the forced air from the fans is ducted.
Dissipation of Heat
from Regulator and
Audio PA
Heat from the audio PA and 9V regulator on the receiver board id
conducted away by a small aluminium heatsink and mounting boss.
The heatsink and boss contact the underside of the board where the
components are mounted and thermal paste ensures a good thermal transfer
between the two surfaces.
Dissipation of Heat
from RF PAs and
Driver
Heat from the RF PAs and driver is conducted to the heatsink through a
copper separator plate. The copper plate is fixed to the underside of the
board and the components soldered directly to it. The copper plate is
mounted directly to the main heatsink boss and a coating of thermal paste
ensures good thermal transfer between these two surfaces.
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